105 [ i75 ] 



In the space of six or seven days, the bodies of the insects requisite 

 to produce only 600 pounds of cocoons, must have lost 700 pounds 

 weight of vapor, or gas, solid and liquid excrcmental substance. 

 This astonishing quantity of substance, execrated from the bodies of 

 the silkworms in so short a time, is of greater weight than the total 

 weight of the cocoons and chrysalis, which only weigh 600 pounds, 

 It is scarcely credible that the bodies of the silkworms should yield 

 so much noxious matter in a few days, were it not demonstrated by 

 positive facts. 



This large body of exhalation, were it stagnant in the laboratory, 

 might, in the later days, generate disorders quickly, and cause great 

 mortality at the very moment when the abundant crop of the cocoons 

 was most confidently expected. We must, therefore, feel tlie deep ne- 

 cessity of attentively following the prescribed directions for avoidins;' 

 *his evil. 



CHAPTER XL 



OP THE SIXTH AGE OF THE SILKWORMS, OR OP THE CHRYSALIS; 

 GATHERING AND PRESERVATION OP THE COCOON. 



The sixth age begins in the chrysalis state, and ends when the moths 

 appear, having left their shell in the cocoon that covered them. 

 The following are the necessary things that remain to be done: 



1. To gather the cocoons. 



2. To choose the cocoons which are to be preserved for the eggs or 

 seed. 



3. Preservation of cocoons until the appearance of the moth; wc 

 shall then treat of 



4. The daily loss of weight which the cocoons sujSer from the time 

 they are finished until the appearance of the moth. 



1. Gathering of the cocoons. 



Strong, healthy, and well managed silkworms, will complete their 

 cocoons in three days and a half at farthest, reckoning from the mo- 

 ment when they first begin casting the flos. This period will be 

 shorter if the silkworms spin the silk in a higher temperature than 

 that which has been indicated, and in very dry air. 



It is also more or less prolonged, if the silkworms are not well and 

 healthy, or if they are exposed to a colder temperature than has been 

 fixed: if they are exposed to transitions of heat and cold, to damp 

 and vitiated air, or to draughts of wind, before the cocoon is sufficiently 

 advanced to shelter them entirely; and, in short, if a great number of 

 silkworms rise long after the first have risen, which is always the can- 

 ;>cquence of bad management and want of care. 



li 



